Arc’teryx Aerios 45 Backpack Review

When I think about the best or most popular backpacks for the lightweight backpacker or thru-hiker crowd, I can rattle off dozens of models from several different brands, no problem.  And while I love the brand for its comfortable apparel, Arc’teryx never made that list.  So when a coworker at REI whispered in my ear about a lightweight, 45-liter backpack coming from their direction, I was skeptical.  Then, after confirming the rumor for myself, I got excited.

New for 2021, the Aerios 45 intrigued me with its running-vest-style shoulder harness and pared-down design.  While it isn’t the lightest backpack out there, I was curious to see for myself how Arc’teryx approached balancing features and weight in a category that is tough to revolutionize.  Not known for producing the lightest gear, Arc’teryx’s stuff is always some of the most comfortable and thoughtfully designed.  Even though the stats of the Aerios didn’t jump out at me, I couldn’t resist the opportunity to see what a lightweight backpack from the masters of comfort could do in the backcountry.  With a great summer planned, I was about to find out.

Arc’teryx Aerios 45 At-a-Glance

Lightweight, comfortable, lots of pockets. There’s more to the Aerios than that, but that’s the gist.

MSRP: $250
Weight: 38 oz men’s, 36 oz women’s
Available sizes: Regular (M’s 18.5”-20.3”, W’s 17”-18.75”), Tall (M’s 19.75”-21.75”, W’s 18.25”-20.25”)
Capacity: 45 liters
Pockets: 1 main, 2 hip-belt, 2 side, external zipper, internal zipper, 4 shoulder
Frame: Internal frame sheet
Material: 100D Cordura nylon, 210D Cordura nylon w/ liquid crystal polymer ripstop
Country of Origin: Philippines

Intended Use

The Aerios 45 is Arc’teryx’s best shot to date at a lightweight, multi-day backpack suitable for thru-hiking.  By eliminating a lot of the extraneous features hefted onto traditional backpacks, they chose to keep things light and simple.  Still, this pack was designed with on-trail efficiency in mind.  With pockets galore, the Aerios holds what you need, where you need it.  The two side pockets hold enough water to cook gallons of couscous, and the running vest-style shoulder harness keeps snacks and essentials in view.  If you like carrying a soft bottle in a shoulder pocket, you can do that too.

All this combines to help keep you on your feet and hiking if you have big miles to cover.  Alternatively, the comfortable carry and low weight are suited to a more leisurely approach as well.  Who said backpacking had to be hard anyway?  Although Arc’teryx does not list a maximum load rating, backpacks of this ilk usually top out around 25-30 pounds.  That’s enough to get an ultralighter very far indeed, or to have a fun weekend with fresh clothes and a chair for lounging in camp.

Circumstances of Review

My Arc’teryx Aerios 45 reached me just in time for summer adventure prime time.  We first became acquainted during a summit of Washington’s Mount Adams, which gave me an opportunity to familiarize myself with the pack’s features and see how it handled an ice axe.

The Aerios endured countless miles of off-balance scrambling across boulders of scratchy granite on the SHR. Photo: SpiceRack

The big test came later, during a 23-day jaunt on the Sierra High Route (SHR) and Southern Sierra High Route (SoSHR).  During this journey, my pack fluctuated from roughly 25 pounds during the short starting section, all the way up to 40-ish pounds for the final haul from Bishop Pass to Horseshoe Meadow.  Of course, these weights dwindled closer to my 17lb baseweight with each passing snack or meal.  With a new synthetic quilt, bear canister, CCF sleeping pad, and solar panel, I was slightly concerned that the 45-liter volume would be stretched too far while including the final section’s 9 days of food.  Sure enough, the Aerios was packed tight, but I got it all in and really put the carrying capacity to the test.

The weather was warm, and the route was rugged.  Bushwhacking through willows and scraping across miles of Sierra granite threatened to shred this pack to tatters.  Yep, the SHR was a great way to test the durability of the Aerios.  And it wasn’t alone.  I had questions about how my body would hold up too.

Arc’teryx Aerios 45 Features

The bungee cord and daisy chain form a versatile system that is great at securing bulky items as long as they are not too heavy. Also notice the roll-top and top zipper pocket. Photo: SpiceRack

Running vest shoulder straps:  The shoulder straps on the Aerios are more like those found on a running vest than typical backpack straps.  They are light on the padding, but above average width to comfortably distribute weight over a wider area.  There are also a ton of pockets.  On each strap, a stretchy mesh pocket can hold a phone or soft flask, and a zippered mesh pocket handles just about anything.  Think snacks, lots of snacks.

Dual sternum strap:  Another feature harvested directly from running vests is the dual sternum strap.  The two shock-cord straps can be adjusted up or down, or removed entirely, to give support where it is needed.  This enables a more customizable fit than the single strap that comes standard on most backpacks.  Also, the stretchy straps don’t restrict breathing even when cinched snuggly.

Huge side pockets:  The two side pockets may be a little funky looking, but they are huge.  Three one-liter bottles easily fit in each side, though most hikers will sub out bottles for other quick-access items.  Average shoulder flexibility allows these to be accessed while keeping the pack on.

Zippered pockets:  The Aerios has two zippered pockets.  A small pocket inside the main compartment secures valuables, and a larger external pocket is a great place to stash often-used small items like a headlamp or sunscreen.  This was my “junk drawer” on the SHR.  At every stop, I was grabbing something from this convenient pocket.

Full-length zipper:  A long side-zipper runs almost the entire height of the Aerios and provides access to the main compartment interior.  This might be useful for some people, but I used it precisely zero times.

Bungee daisy chain:  Instead of the classic rear mesh stuff pocket, the folks at Arc’teryx lashed on a crisscrossing bungee to the back of the Aerios.  This won’t hold small items secure, but bulky things have a home here.  My foam sleeping pad and bag of chips stayed secure over many rough miles.

Roll-top closure:  The tried and true method of closing a backpack helps keep contents tidy and compressed no matter how full the load.  It also provides reasonable weather protection on a pack that has no top lid.  It kept my stuff dry during all but the most punishing thunderstorm.

AeroForm back panel:  The Aerios uses a plastic frame sheet to transfer weight to the hips and prevent barreling.  Dimpled mesh stuff on the back contact surface allows for some air flow despite the close-fitting design.  While not as breathable as my full-suspension pack, I noticed during a Sierra heatwave that the Aerios was less sweat-inducing than my other lightweight packs.

How’d it do?

It was a risk trusting a dream trip to an unfamiliar backpack, and the Aerios rewarded my optimism with a comfortable three weeks in the Sierra that left me with very little to complain about.  Generally, the pack handled the tough, rugged, and scrambly route without issue besides losing a water bottle out of a side pocket during a sketchy climb.

The Highlight

That shoulder harness is the standout highlight of the Aerios. Regular backpack straps feel like a wasted opportunity now. Photo: SpiceRack

The shoulder harness was the highlight and I quickly became enamored with not just the comfort of the thin-yet-wide straps, but also the four pockets that kept a million things on hand.  On most days I stuffed them with my phone, headnet, chapstick, a packet of gummies, and four bars to snack on.  Before the lid busted, I also carried a 500ml soft bottle on my right shoulder.  That’s a lot of stuff, and combined with what I also crammed into my hip-belt, I was able to cruise without taking off my pack for hours at a time.  This was especially welcome on sketchy terrain when ground stability and balance were not givens.  Increasingly, pack designers are including pockets on the shoulder harness.  Now I understand why.

Weight Capacity

The Aerios carried up to 30-35 pounds in relative comfort.  Obviously, I preferred carrying closer to 25lbs.  When I pushed it to 40lbs, my shoulders became noticeably more fatigued.  No surprises there.  Had I been able to tighten the hip belt further (I was bottomed out), I think that my shoulders would have fared better.  As it was, the wide shoulder straps did a commendable job making up for the belt’s shortcomings.

The volume and construction of this pack are well matched.  The plastic frame sheet is lighter-duty than traditional metal stays, and the 45L volume naturally limits how much it is possible to carry.  Only when overstuffing with heavy food was I able to push the Aerios beyond its comfort limit.

Things I Missed

I’m all about breaking free from the mold and Arc’teryx did a good job of designing a unique pack that diverges from the traditional ultralight big-tube-with-two-side-pockets-and-a-mesh-pocket style.  That said, I missed a couple of the familiar features that a lot of us in the thru-hiking community now take for granted.

The Aerios offers alternatives to the mesh pocket, matched roll-top buckles, and top strap, like the bungee holding on my pad. Everything works out, but I miss them anyway. Photo: SpiceRack

Mesh back pocket

A large, stuffable rear mesh pocket is one of the most useful features on my favorite backpacks.  Even the ultralightest of the ultralight packs incorporate this versatile pocket.  For some reason, the Aerios doesn’t have one.  To be fair, the crisscrossing bungee that the Aerios uses instead did a great job holding my CCF pad.  Also, all the other things that I would normally keep in the absent mesh pocket found new homes in either the zippered outer pocket or supersized side pockets.  So it worked out, but I still miss that mesh.

Matched roll-top buckles

The buckles on the roll-top closure are not a matched pair (both female), meaning that they do not buckle together.  That is fine most of the time when cinching the top down with the side straps as designed, but on rare occasions, I just wanted to snap the top buckles together and couldn’t.  Switching the buckles top and bottom on one side would be an easy way for Arc’teryx to add versatility at zero cost.

Top strap

A single adjustable strap over the top of a pack is one of the only ways to secure bulky items to a lightweight pack, especially if they are heavy.  On many trails, it is common to see a CCF pad flopping up and down on top of a pack with each stride of a passing hiker.  Bear canisters also settle here, free from the hassle of packing an awkward barrel and providing easy access to snacks.  I learned from my partner, SpiceRack, that the top strap is really a chip strap.  Now I never leave town without a bag of BBQ Lays or Ruffles All Dressed displayed like a bumper sticker.  This changed with the Aerios, which has no chip strap.  The bungee system picked up the slack, but with less security.

Light, but could be lighter.

At just 38 ounces, the Aerios is a lightweight backpack, no matter how you look at it.  There are lighter packs with a similar feature set, but the Aerios is extremely durable for the weight and the included shoulder strap pockets eliminate the need to find a costly ($ and ounces) aftermarket solution.  I also appreciated the two zipper pockets for giving important things a safe home.

The shoulder pockets and durable fabric are worth their weight. That full length zipper? Not so much. Before you get on me for complaining about a zipper while carrying a toy, the pinwheel actually makes my pack lighter. Don’t ask me how.

However, there was one zipper I think the Aerios would be better off without.  The full-length zipper seems to me an unnecessary durability risk and wasted ounce.  In a pack this small it is hard to lose items to the extent that zipping it open like a tauntaun is necessary.  The roll-top closure provides more than adequate access to the main compartment.  It’s easier to close up, to boot.

While this pack could definitely be a few ounces lighter, besides that zipper, paring it down would eliminate the features that make it great to begin with.  Durability and convenience are a priority with the Aerios.  If those are priorities to you, the extra ounces are worth it.

Arc’teryx Aerios 45 Pros

The shoulder pockets and huge side pockets combine with the hip belt to carry a ton of stuff within easy reach. Easy snacking. Photo: SpiceRack

Shoulder harness:  Not only are the wide shoulder straps super comfy, but the extra pockets really improve hiking efficiency.  Combined with my hip-belt pockets, I had plenty of room to carry an entire day’s worth of snacks within easy reach.  I also had space to hold my phone and bug head-net in one pocket and a .5-liter soft bottle in another.  Even fully stuffed, the shoulder straps did not feel unwieldy, nor did they get in the way during hands-on scrambles.

Stretchy sternum straps:  Turns out, using stretchy shock cord for the whole sternum strap is a great idea.  Even when I cinched the two cords tight for extra stability, I could take full deep breaths, feeling the elastic expand with each inhale.  With two sternum straps, each one carries less load which allows them to be made using a more comfortable material.

Zippered pockets:  I’m a sucker for a zippered pocket to keep my small things organized.  Especially in the absence of a rear mesh pocket, I found the two pockets on the Aerios to be just what I needed to keep important items organized and accessible.  My wallet and keys stayed secure in the internal pocket, while the outer pocket held my headlamp, water filter, sunscreen, trowel, head net, external battery, and some snacks.

The side pockets hold a ton of stuff, which is great, but as I learned on the SHR, stuff can fall out when hands touch the dirt. Photo: SpiceRack

Huge side pockets:  The massive side pockets swallowed tons of gear when I got too lazy to properly stow things inside the pack.  I easily fit my three water bottles, cold-soak jar, tent poles, maps, and wind jacket between the two pockets.  The pockets were not the most secure (I lost a water bottle twice when scrambling), but for classic on-trail hiking this won’t be an issue.  A little more depth would lock things in.

Roll-top closure:  This backpack closure method provides weather protection, compression, and unparalleled adjustability relative to cinch-top closures.  To a certain extent one can adjust the pack capacity to match what is being carried.  The Aerios looked composed both stuffed with nine days of food and when my food bag was running on empty.  

Durable:  Despite the Aerios being a lightweight backpack, the fabric handles abuse.  Unlike the material on some ultralight backpacks, the 100D nylon does not need to be babied in any way.  Official jargon credits this to a “liquid crystal polymer ripstop”.  I’m not sure if crystals are really necessary on a backpack, but the fabric shrugged off daily abuse on extremely rugged terrain.  No complaints here.

Arc’teryx Aerios 45 Cons

Oh those sternum straps. So comfy, yet so impossible to keep tight. Photo: SpiceRack

Limited sizing:  This pack is only offered in two sizes, Regular and Tall, which excludes those backpackers with a shorter torso.  While there is not officially a way to adjust the torso length, I found reasonable success by adjusting the balance between shoulder strap and load-lifter tightness.  Tightening the load lifters first lengthened the torso.  Tightening the shoulder straps first shortened it.  Mess around with it.

Lacking compression:  The Aerios doesn’t have your typical side compression straps to keep small loads stable.  The roll-top closure allows for some top-down compression, but that doesn’t achieve the same reassuring, close-to-body feeling when cruising those last few miles to town with an empty food bag.  The rear bungee system is capable of scrunching up some of the extra pack space, but no-stretch webbing is a better tool for this job.

Loosening sternum straps:  I wanted to love the comfortably stretchy sternum straps unconditionally, but I could not keep them tight.  Seriously, within five minutes of tightening, they would loosen up.  The locking mechanism isn’t up to the task.  The pack was still comfortable, but I was constantly yanking on the sternum strap adjustment cords to keep them snug.

Hip-belt minimum:  Even the fully-tightened hip-belt was not quite tight enough for me.  Sure I’m skinny, but not extremely, and I know at least a few thru-hikers who are even narrower than I am.  Transferring load from shoulders to hips is important, and this will be difficult for anyone with a 30-inch or smaller waist, at least with the pack I tested (men’s regular).

Final Thoughts

How to sum up my thoughts on the Arc’teryx Aerios 45? By the end of the SoSHR, I’d concluded that it is a weird, yet very comfortable pack. Photo: SpiceRack

The Aerios 45 is a weird backpack.  It looks a little funky, takes a little bit of learning to figure out, and does things its own way.  My biggest gripe is about the features it is missing, like a big mesh pocket.  However, the Aerios just operates differently than the tried and true ultralight pack design, and when I opened up to this divergence, I came to appreciate what it does offer rather than dwell on what it doesn’t.  It carried all my stuff comfortably and efficiently, which is really what it is all about.

The shoulder harness opened my eyes to the seemingly limitless utility of having beaucoup pockets running shoulder to hip.  More importantly, it was supremely comfortable right up until the point I overloaded the pack.  The perfectly executed zipper pockets soothed my anxiousness about keeping all the important little things safe and organized.  In the end, the Aerios folded seamlessly into the narrative of a fantastic summer adventure.  That’s what good gear is all about.

Shop the Men’s Arc’teryx Aerios 45

Shop the Women’s Arc’teryx Aerios 45

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Disclaimer: The Arc’teryx Aerios 45 was donated for the purpose of review

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